Grinding tool for extremely hard alloys



Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE GRINDING TOOL FOR EXTREMELY HARD ALLOYS No Drawing. Application August 2, 1933, Serial No. 683,408. In Germany June 12, 1933 8 Claims.

This invention relates to grinding tools of the kind which are adapted for working extremely hard alloys.

Recently quite a number of very hard alloys have been developed which are especially adapted for the manufacture of tools of all sorts. These valuable materials, as for instance the socalled Wimet steel, which are almost as hard as corundum, cannot be ground properly and completely by the usual lapping wheels of silicon carbide on account of the insufl'lcient hardness of the abrasive material used in. the latter. Therefore it has been proposed to use diamond for such grinding purposes. Lapping wheels having metal bodies embedded with diamond grains or diamond dust bound together with terracotta or with sintered alloys of all kinds have been put on the market. -Such grinding tools are all very expensive because of the high cost of their manufacture. The high temperature used in the manufacture of such grinding tools often will impair the abrasive qualities of the diamond grains.

A great disadvantage of such lapping wheels containing diamond as the only abrasive agent consists in their rough or ripping action. For certain grinding purposes the admixture of silicon carbide powder as a less hard abrasive material with the usual diamond dust has been proposed but this mixture has so far never been used for the manufacture of grinding tools.

On the other hand it has been proposed to manufacture grinding tools by combining known abrasive agents such as corundum, silicon carbide, emery, diamond etc., with artificial resins, especially with phenol resins. Such grinding tools are rather brittle and very easily become soft and sticky by the heat developed during the grinding operation.

The object of the present invention is to provide a grinding tool for extremely hard alloys which has none of the above stated disadvantages. This tool contains a homogeneous mixture of diamond and silicon carbide powder as abrasive materials, a liquid artificial resin as binding material, graphite dust to reduce the rough action of the hard abrasive agents, and a pulverulent artificial resin to increase the solidity, to reduce the brittleness and to prevent the mass from clogging. Furthermore this mixture may contain fibrous materials such as cotton wool which will give the artificial resin binder combination a greater solidity and elasticity.

This novel mixture allows the manufacture of grinding tools of presently unknown efllcacy regarding their grinding power, smooth action and little wear. Such grinding tools increase considerably the possibilities of use of the high grade hard metals which are otherwise very difficult to work.

A grinding tool according to the present invention may for instance be manufactured as follows:-

Approximately equal parts by weight of diamond and silicon carbide powder having the 10 same granularity (passing through a sieve havingabout 150 to 200 meshes/cm.) a greater part of graphite dust, a small quantity of pulverulent artificial resin, and a relatively great quantity of liquid phenol resin are thoroughly mixed to- 15 gether at a temperature of C. The mixture becomes at the end a pasty homogeneous forming mass. After having admixed fibrous materials such as cotton wool and after a previous heating up to 80 C. during about twelve hours 20 the mass is filled into the desired moulds, with or without the insertion of metal discs, paper discs, wire tissues, etc., as reinforcements, and is heated under pressure at a temperature of 170 C. According to the size of the moulds this heat- 25 ing is stopped sooner or later and the molded piece is left to cool.

Immediately after this cooling, the tools may be used However, for certainpurposes, tools with a stronger binding are required, which are 30 obtained by a subsequent hardening process consisting in a longer heating at C. of the -molded pieces.

What I claim as new is:

1. A method of making abrasive articles which 35 comprises forming a mixture of approximately equal parts of diamond powder and silicon carbide powder, graphite dust, pulverulent potentially reactive resin and liquid potentially reactive resin at a temperature of approximately 40 100 0., whereby a pasty mass results, heating the pasty mass to 80 C. for a period of approximately 12 hours, and heating the thus-treated mixture in a mold to a temperature of approximately 0. 45

2. A composition of matter comprised of diamond granules, manufactured abrasive granules of a hardness less than 10 on Mohs scale, graphite, and resin, said ingredients being thoroughly intermingled and hardened by the application of 50 heat and pressure. r

3. A composition of matter comprised of diamond granules, manufactured abrasive granules of a hardness less than 10 on Mohs scale, and graphite, said ingredients being bound together 55 by and homogeneously dispersed in a hardened synthetic resin resulting from treatment by heat and pressure of a combination or liquid and powdered potentially reactive synthetic resin.

4. A composition of matter comprised of diamond granules, manutactured abrasive granules of a hardness less than 10 on Moh's scale, synthetic-resin, graphite, and fibrous filler, the intimate mixture of said ingredients being hardened by heat and pressure.

5, An abrasive tool comprising a molded homogeneous mass of diamond granules, silicon'carbide granules, graphite, and powdered synthetic resin bound together by a hardened synthetic resin.

6. An abrasive tool comprising a hard molded bodyoi' a synthetic resin having a mixture of substantially equal parts by weight of diamond and silicon carbide granules, graphite dust, and

a pulverulent synthetic resin homogeneously dispersed therein.

7. An abrasive tool comprising a molded synthetic resin body resulting from the treatment by heat'and pressure of a mixture of liquid and powdered potentially reactive synthetic resin,

and having homogeneously dispersed therein a mixture of approximately equal parts of diamond powder and silicon carbide powder, and graphite dust.

8. An abrasive tool comprising a molded synthetic resin body resulting from the treatment by heat and pressure of a mixture 01' liquid and powdered potentially reactive synthetic resin, and having homogeneously dispersed therein diamond granules, manufactured abrasive granules 01a hardness less than 10 on Mohs scale, and graphite.

, PHILIPPE VOEGELI-JAGGI. 

